1. Field of the Invention
This invention relates to an image reading apparatus, an image forming apparatus, and an image reading method, each capable of efficiently reading image data by a “sheet through method.” The image reading apparatus may determine a temporary size for the image printed on an original fed by an automatic document feeder (hereafter, referred to as an “ADF”).
2. Description of the Related Art
Recently, image forming apparatuses such as digital copying machines have improved in performance. Demand is increasing for apparatuses that include an ADF and read image data by the sheet through method.
In the sheet through method, an original is moved over a scanner wherein the scanner is held in place. The image forming apparatus reads image data from the original. The sheet through method differs from the ordinary original scanning method. In an ordinary scanning method, the scanner moves to read image data from an original where the original is on the original table. The sheet through method can read the image data faster than the original scanning method. This is because it omits the time consuming process of placing the original on the original table and then moving the scanner below the original table.
Jpn. Pat. Appln. KOKAI Publication No. 11-187207 discloses an image reading apparatus that performs the sheet through method. The apparatus has an ADF and a charge coupled device (CCD). The ADF feeds an original to the CCD. The CCD is a reading unit held in place. The CCD determines the width of the original when the ADF feeds an original to it. From the width of the original, thus determined, the size of the original can be inferred. For example, if the width is that of A4 size paper sheets, then it is inferred that the original is an A4 size sheet. Hence, the user need not input the data representing the size of the original.
The image data read by the CCD is stored in a memory region. Thereafter, a data file is generated from the image data and recorded on a hard disk or the like. Thus, the apparatus may read the image data from the original, even if the user does not input the data representing the size of the original.
The conventional image reading apparatus can efficiently read the image data from the original even if the user does not input the original size data, as long as the original is of a standard size such as A4 size. When originals of different sizes are stacked on the ADF, however, the CCD fails to determine the size of each original. Consequently, the data file generated from any item of image data read by the CCD from an original sheet may not correspond with the size of another original sheet. This may cause troubles in storing the image data, resulting in inefficient filing and printing of the image data.